ABSTRACT A decade and a half of rapidly increasing use of and geographic penetration of methamphetamine (MA) across the U.S. and the consequences of its use have generated concern and increasing efforts to improve interdiction, prevention, and treatment strategies, with a priority on research to inform these strategies. Limited information is available regarding the life course of MA abuse, particularly as MA users age. Further research is needed to provide empirical support for developing strategies to address issues specific to older users. The proposed project is a follow-up of 596 previously studied MA users, half recruited from drug treatment participation, half from the same communities but with no prior treatment for MA use at recruitment. The project will collect data using the Natural History Interview to add an average of 8 years of detailed histories on substance use, treatment, and criminal careers of these MA users; these new data combined with previously collected data will produce life course trajectories averaging at least 28 years in duration, covering teen and adult periods. Additional data will come from administrative records from several state agencies. The sample is 35% female/65% male, 33% Hispanic/38% non-Hispanic White/17% African- American/12% other ethnicity. Subjects will range in age from about 28 to 74 (average 42) at beginning of the follow-up study. Analyses will describe the current status and extended MA use histories, examining patterns of MA and other drug use, including escalation, deceleration, and possible cessation and recovery; examine drug treatment utilization patterns and relationship to MA use patterns; and determine health morbidity and mortality and assess differences between surviving and deceased users. The study will also assess the long-term outcomes (14 or more years) of a previously identified drug treatment episode (for the subsample recruited from treatment). In addition, the study will estimate cumulative social costs of MA abuse for the sample in terms of criminal activity, incarceration, drug treatment services, health and mental health services, and welfare system participation; and it will examine differences in costs related to distinctive patterns of MA use and user characteristics. Analysis methods will include growth models and growth mixture models to assess MA use trajectories and their relationships to services utilization, other events, and selected user characteristics.